1. Field of the Invention
The present invention relates to a swash plate compressor with a crank chamber adapted for use in a vehicle air-conditioner. In particular, the invention relates to a swash plate compressor with a crank chamber, which contains the movement of pistons during each suction and discharge stroke, while suppressing noisy vibration of the pistons.
2. Description of Related Art
Swash plate compressors are known in the art. The structure of a known swash plate compressor includes a closed, cylinder casing assembly bracketed by a front housing and a cylinder head, and such compressors are provided with a cylinder block at a cylinder head side and a hollow portion, such as a crank chamber. The cylinder block has a plurality of annularly arranged cylinders within which pistons slide. A drive shaft is rotatably supported by the central portion of the cylinder block and the front housing. A swash plate is connected to the drive shaft at predetermined angle. Pistons, which are operably connected to the swash plate by means of shoes, reciprocate within cylinders. Each piston has a head portion at one end and a skirt portion at another end.
In operation, the drive shaft is rotated by the engine of a vehicle through a pulley arrangement. The rotation of the drive shaft is transferred to the swash plate, so that, with respect to the rotation of the drive shaft, the inclined surface of the swash plate moves axially to the right and left. As pistons reciprocate, refrigerant gas, which is introduced into a suction chamber from a fluid inlet port, is drawn into each cylinder and compressed. Pistons are prevented from rotating because they abut an inside surface of the crank chamber thereof at the skirt portion. The compressed refrigerant gas is discharged to the discharge chamber from each cylinder through a discharge port and therefrom into an external fluid circuit, for example, a cooling circuit, through the fluid outlet port.
There is a very small clearance in a sliding surface between the head portion of the piston and the cylinder, within which a lubricating oil film is retained. When each of the pistons approaches a bottom dead center and the length of the sliding surface between the head portion of that piston and the cylinder becomes small or reaches a minimum, the restriction of the free movement of that piston caused by the cylinder, eases. There also is a very small clearance in the sliding surface between an outside surface of the skirt portion of the piston and an inside surface of the crank chamber. When the restriction of the free movement of the piston eases, the skirt portion of the piston is drawn in the direction of the rotation of the swash plate. Therefore, the piston tends to slant in the direction of the rotation of the swash plate and against the sliding surface between the head portion of the piston and the cylinder. Consequently, the pistons may nutate, and as a result, the pistons may vibrate, and compressor noise may increase.
An object of the present invention is to eliminate or reduce the above-mentioned defects encountered in known swash plate compressors having a crank chamber and pistons.
Another object of the present invention is to provide a swash plate compressor adapted to be used for forming a quiet, vehicle air-conditioning system.
In an embodiment of the present invention, a swash plate compressor comprises a cylinder block having a plurality of cylinders positioned therein, a crank chamber, a suction chamber, and a discharge chamber. Each of the plurality of pistons has a head portion and a skirt portion. The head portion of the piston is slidably disposed within one of the cylinders. The skirt portion of the piston slidably abuts on an inside surface of the crank chamber that prevents the pistons from nutating. For example, the reciprocating motion of a skirt portion of each piston in a direction tangential to the circumference of the swash plate or the rotation of the pistons about their axes, or both, is prevented. A drive shaft is rotatably supported in the cylinder block. A swash plate is disposed in the crank chamber and is tiltably connected to the drive shaft. A bearing couples the swash plate to each of the pistons, so that the pistons are driven in a reciprocating motion within the cylinders upon rotation of the swash plate. The crank chamber has a truncated cone-shape having an oblique angle, such that an inside diameter of the crank chamber decreases between a top dead center and a bottom dead center of the piston.
Other objects, features, and advantages will be apparent to persons of ordinary skill in the art from the following description of the invention with reference to the accompanying drawings.